Rosin esters, including rosin esters derived from polyhydric alcohols, have been known for more than 50 years. See, for example, U.S. Pat. No. 1,820,265 to Bent, et al. Rosin esters are typically formed by the reaction of rosin, which is primarily a mixture of isomeric C20 tricyclic mono-carboxylic acids known as rosin acids, with alcohols such as glycerol or pentaerythritol. The resultant rosin esters serve as additives in a variety of applications, including as tackifiers in hot-melt and pressure-sensitive adhesives, modifiers for rubbers and various plastics, emulsifiers for synthetic rubbers, base materials for chewing gum, resins in coating compositions such as traffic paints and inks, and sizing agents for paper making.
While suitable for many applications, many existing rosin esters fail to possess suitable properties for particular applications. Notably, many commercially available rosin esters are colored (e.g., yellow or yellowish brown) and exhibit poor oxidative stability. Furthermore, many existing rosin esters do not comply with current regulatory standards for use in food packaging applications. In addition, the balance between tack, peel, and shear properties of many existing liquid rosin ester-based pressure sensitive adhesives (PSAs) is not optimal. Finally, many existing rosin esters are relatively polar compounds that may be incompatible with less polar polymers, such as polyolefins. Accordingly, there continues to be a need for rosin-based compositions which exhibit improved properties.